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module DataMapper
  module Is
    module Accessible
      def is_accessible
        include InstanceMethods
        property :created_id, Integer

        belongs_to :created_by, :class_name => "User", :child_key => [:created_id]
        has n, :accessors, :through => Resource, :class_name => "User"

        attr_accessor :accessor_ids
        attr_accessor :current_user

        before :create, :init_accessors
        before :save, :add_accessors
      end

      module InstanceMethods
        def viewable?(user = nil)
          return false if accessors.empty?
          user ||= current_user
          accessors.include?(user)
        end

        def init_accessors
          unless @current_user.nil?
            self.created_by = @current_user
            self.accessors << @current_user 
          end
        end

        def add_accessors
          unless self.accessor_ids.nil?
            self.accessor_ids.split(',').each{|user_id| accessors << User[user_id]}
          end
        end
      end
    end
  end
end

DataMapper::Resource::ClassMethods.send(:include, DataMapper::Is::Accessible)